Presidents, as Donald Trump has learned to his dismay, have to deal with many checks on their power, including a bothersome Congress and Supreme Court.

But the constitutional pardon power “cannot be fettered by legislative restrictions,” the Supreme Court ruled in 1866. Trump, clearly fascinated by that notion, has in recent weeks been bestowing clemency at his whim, like a benevolent monarch.

Last week, Trump's pardon of two Oregon cattlemen — who'd become symbols of the battle between Western ranchers and the federal government over grazing lands — shocked even the men's lawyer, who couldn't figure out how it happened.

Turns out the men, serving five-year terms for starting fires that damaged federal lands, had a friend in high places: Forrest Lucas, an Indiana multi-millionaire and longtime friend and donor to Vice President Pence, who pleaded their case.

That surprise followed a flurry of scattershot pardons to controversial allies (former Arizona sheriff Joe Arpaio) or people whose causes were championed by associates or celebrities (the late boxer Jack Johnson).

The pardon power gives presidents the unique ability to right injustices and provide deserving people with a chance to rebuild their lives. As such, it needs to be exercised using a process that is rational, just and orderly. But Trump, as is his custom, has bypassed the Justice Department pardon advisory program and is handing out pardons randomly.

The fear is that Trump is signaling to former campaign manager Paul Manafort, and other former aides who’ve been indicted, that he will step in to rescue them — a strong incentive for them not to cooperate with special counsel Robert Mueller. And the worst fear? That Trump will try to pardon himself, making a mockery of the system of justice that has guided the country for nearly 230 years.

He has already said that he can pardon himself (but doesn't need to). This seems highly unlikely, but the proposition has never been tested in court.

Trump isn’t the first president to use his power of clemency — which includes commuting sentences or pardoning people convicted of crimes — in controversial or abusive ways. President Ford pardoned Richard Nixon before the disgraced president was indicted, and George H.W. Bush pardoned Ronald Regan's Defense Secretary Caspar Weinberger. President Clinton’s pardon of fugitive financier Marc Rich smacked of corruption, coming as it did after Rich's ex-wife had donated $450,000 to Clinton's presidential library foundation.

A more prevalent problem is that most modern-day presidents have been stingy with clemency, even as harsh federal sentencing guidelines have left many non-violent first offenders to languish in federal prisons. It took President Obama until the middle of his second term to start exercising his clemency muscles for such prisoners. He ultimately granted clemency to a record 1,715 prisoners and pardoned 212 people.

Trumps’ commutation for Alice Marie Johnson — a 63-year-old woman who had served 21 years of a life-without-parole sentence for a non-violent drug conviction — does not appear abusive. Critics have seized on the fact that Johnson's case was championed by reality TV star Kim Kardashian. But if Kardashian wants to put her celebrity to good use, that’s fine.

The real question is whether Trump’s mercy will flow to other little-known prisoners who deserve it or only to those with a measure of fame or who catch the eye of a celebrity.

Trump has gotten off to a messy start, and threatens to take pardon abuse to new levels. But his romance with the pardon power has potential to be turned into a powerful force to temper injustice in the justice system.

That’s why talk of amending the Constitution to rein him in is premature. Amending the Constitution is extremely difficult, and for good reason. It should be done rarely and to right enormous wrongs. The way to rein in an irresponsible president is through impeachment or the ballot box, not by changing the nation's founding document.